Diffusion of benzene and tetrachloroethylene through saturated cement paste

Abstract

Diffusion of highly volatile organic compounds (VOCs) through buried concrete infrastructure components, such as pipes and culverts, can occur if these components come in contact with contaminated groundwater or soil. Among various VOCs, benzene and tetrachloroethylene (PCE), are the most common contaminants. This paper aims at measuring the effective diffusion coefficients of benzene and PCE in cement paste. The free diffusion coefficients of VOCs in simulated pore solution were also measured and used in empirical models.Results show that VOCs diffusion coefficients decreased with decreasing w/c because of reduced porosity and increased tortuosity of the pore network as well as increased ionic strength of the pore solution. The increased ionic strength of the pore solution reduced the solubility limit of VOCs in the pore solution and decreased the free diffusion coefficient of VOCs in the pore solution. Also, among all models, phenomenological model provided the most accurate estimates.